By Thomas Escritt and Steve Holland
THE HAGUE (Reuters) - U.S. President Barack Obama brought together the leaders of Japan and South Korea on Tuesday for their first face-to-face talks, seeking to thaw chilly relations between two of Washington's closest Asian allies.
The United States hopes the move may improve the bilateral relationship between Seoul and Tokyo, clouded by resentment over Japan's colonial past, and strengthen their combined response to regional concerns such as North Korea and China.
Obama, speaking after meeting both leaders on the sidelines of a nuclear security summit in The Hague, said the three countries had presented a united front against the threat posed by the nuclear ambitions of North Korean leader Kim Jong-un.
Pyongyang's "provocations and threats" will be met by a united response, said Obama, who will visit Japan and South Korean in April. "It is the first time that the three of us have an opportunity to meet together (on) some serious challenges that we all face," he said.
South Korean President Park Geun-hye and Japanese Prime Minister Shinzo Abe, who also attended the two-day Nuclear Security Summit, emphasized a need to work together on containing the North Korean nuclear threat.
"Over the last five years, close coordination between our three countries succeeded in changing the game with North Korea: our trilateral cooperation has sent a strong signal to Pyongyang that its provocations and threats will be met with a unified response," Obama said.
The three leaders discussed "specific steps to deepen that coordination", including "military cooperation that includes joint exercises and on missile defense," he said.
Japan is to hold high-level talks with North Korea over Pyongyang's nuclear and missile programs next week.
"Given the increasingly uncertain developments in North Korea, the critical need for closer coordination among the three counties with regard to the North Korean nuclear issues, the chance to engage in an exchange of views with president Obama ... is very significant," Abe said.
"This meeting will offer us a chance to reaffirm our trilateral coordination and strength and cooperation on the nuclear front," Abe said.
But ties between the Asian neighbors have been chilly due to anger in South Korea that Japan's leaders have not atoned for their country's wartime aggression, including the use of Koreans as sex slaves, and to territorial disputes over islands in the sea between them.
"In a relationship between countries there are always challenges," Japan's Abe told reporters earlier on Tuesday. "Thanks to President Obama we are scheduled to conduct a frank exchange of opinions with Obama and Park on security in East Asia."
Though Abe, elected in 2012, has long sought a meeting with Park, his approaches have been "clumsy" in the context of the sensitivities surrounding Japan's colonial history, said John Swenson-Wright of the foreign affairs think tank Chatham House.
"This is partly the result of attempts by the U.S. to engineer a mechanism by which Abe and Park might meet," he said.
Some of Abe's gestures at home, such as visiting a shrine to Japan's war dead including former Japanese leaders and generals convicted of war crimes in northeast Asia, have caused offence in Korea.
Abe's attempts to seek support from South Korea for a common stance towards China, the regional giant, have also been thwarted by Park's own moves to develop a closer relationship, Swenson-Wright said.
China is almost alone in having significant influence over North Korea's leadership.
"I told (Chinese president) Xi Jinping I would like to return to a mutual beneficial relationship in St Petersburg last year," Abe told journalists in The Hague. "Since then I regret we have not had the opportunity to have a deeper exchange of views."
(Editing by Anthony Deutsch/Ruth Pitchford)